SubPos

Wi-Fi Indoor Positioning

One of the most straightforward uses of beacon technology is to create indoor positioning systems — networks of beacons in fixed, known locations that can give a sense of where a device is located when signals from GPS satellites are blocked. Bluetooth has so far dominated the beacon arena, but Wi-Fi is in pursuit with Wi-Fi Aware bringing beacon-like upgrades to the base protocol and, now, the open-source SubPos project.

Designed to run on existing Wi-Fi base stations alongside purpose-built nodes, SubPos improves on traditional Wi-Fi positioning techniques that estimate location based on the relative strengths of the signals from nearby access points. Instead, SubPos embeds positioning information in the “frame” broadcast by each node — which is the one-way ping that Wi-Fi base stations already use to advertise their presence to nearby devices.

A SubPos node’s frame might include its absolute position in latitude and longitude, which would allow the data to integrate with existing mapping apps. Or it might include a relative position of just an X,Y coordinate, which an app could compare to an arbitrary preset zero point on, say, the floor plan of a building.

When devices know not only the strength of every nearby signal, but also their exact origin points, they can triangulate their own positions much more accurately. In tests, SubPos has already demonstrated accuracy down to the nearest half-meter. And the more beacons that are installed in a particular location, the better the calibration can be.

Best of all, the whole setup requires no outside data connection — as long as the nodes have power and the receiving device has a local copy of the relevant maps or floor plans, SubPos can function as a self-contained system.

The SubPos standard is open-source, as are the designs for the standalone node hardware, which are built around the low-cost ESP8266 Wi-Fi module. The project also includes a simple API for software developers to integrate SubPos beacons into their apps.